A videoconferencing system is a technology to conduct videoconferences via communication networks such as the Internet. Owing to recent demand for reducing time and expenses for business trips, such a videoconferencing system is becoming increasingly popular. In the videoconferencing system, the videoconference may be implemented by transmitting and receiving telecommunication data such as image data and audio data between two or more terminals at different locations.
In a case where the two terminals at different locations start communicating, and the communications are conducted via Internet Protocol (IP) telephones (i.e., one of phone services), the Session Initiation Protocol (SIP) is generally utilized as a communication protocol to establish a session between the terminals at two different locations. With this type of communication protocol (i.e., SIP), the SIP server controls a call between the communication terminals (i.e., a call is established between the terminals by exchanging call information between them). Once the session has been established between the communication terminals, they are instantly in communication, such as transmitting voice data, with each other. However, since the SIP is designed as the communication protocol specifically to control a call or a communication session between the two locations (i.e., two terminals), the SIP may not control calls among more than two locations (i.e., two or more communication terminals).
U.S. Pat. No. 7,631,039 (hereinafter called “Patent Document 1”) discloses an example of a related art technology for initiating a videoconference among terminals at more than two locations. This technology utilizes an allocator that determines conference information indicating a conference attribute. Specifically, in the technology disclosed in Patent Document 1, two or more clients receive the conference information determined by the allocator. These clients are each connected to a multipoint conference unit (MCU) that relays communication data including audio data and image data based on the received conference information. When the MCU has been connected to each of the clients, the MCU relays the communication data received from the clients to the other clients. As a result, a videoconference may be initiated among the clients (terminals) located at more than two locations.
However, in the related art videoconference system, a management system utilized for controlling communications among videoconferencing terminals may not manage communication statuses of the videoconferencing terminals. Accordingly, when the management system transmits information desirable for initiating the communications to destination videoconferencing terminals, connections between the videoconferencing terminals may not be established due to engagement of the destination videoconferencing terminals with other videoconference terminals. That is, in the related art technology, the management system does not detect communication statuses of the destination videoconference terminals before transmitting the information desirable for initiating the communications to destination videoconference terminals, and therefore, the management system may not effectively control the connections among the videoconference terminals.